1918 ' J Camebon, Swainson'a Hawk in Montana. 391 



Foi urn Male Plumage. 



In the fourth male plumage which resembles the third, and bears 

 the same relation to it as the second does to the first, the bird be- 

 comea lighter everywhere. The whole of the underparts are white, 

 and the broad cinnamon band of the upper breast is reduced to a 

 narrower one of white-spotted chestnut, against which the immacu- 

 late white throat is less sharply defined than in the third plumage. 

 The head is smoke color, or ashy, the occiput white, and the upper 

 parts always, in my experience, either pale buffy brown, brownish 

 ash, or bluish ash, but never dark brown as described by some 

 ornithologists. 



In Fisher's 'Hawks and Owls of the United States,' p. 78, 1S93, 

 Knight's 'Birds of Maine' (p. 230, 1908), and Knowlton's 'Birds 

 of The World' (p. 257, 1909), one plumage phase of the normal 

 adult male is, in my opinion, correctly given as "grayish brown," 

 but no reference is made in ornithological works to the other color 

 forms of bluish ash and bully brown. Dr. Jonathan Dwight, Jr. 

 was good enough to comment on a paper of mine on the plumage of 

 B. swainsoni published in 'The Auk' (Vol. XXV, p. 468), remark- 

 ing in ' Bird Lore' (Vol. X, p. 267): "The gray birds may change 

 to brown through wear just as the loss of the "frosting" of some 

 Terns' feathers produces blacker wings." I have myself come to 

 the conclusion that this is probably what occurs, and that from the 

 effects of wear and light on the feathers the ash colored birds be- 

 come browner. I am the more inclined to adopt this view because, 

 as above mentioned, in all specimens examined by me the tail has 

 faded to brownish whenever exposed to weather or light, while its 

 covered portions retain their pristine ash or slate-color untarnished. 

 Otherwise the three color forms of bully brown, bluish ash, and 

 brownish ash can only be explained by dimorphism. As Swainson's 

 Hawk is so widely distributed in its breeding range, which extends 

 from Alaska to Chile, normal adults from different localities might 

 easily differ in the color of the mantle. The discoveries of Dr. 

 J. A. Allen on the relations between locality and coloration in 

 American animals, from North to South, will at once come to mind, 

 as hi> remarks have been freely quoted by most naturalists. He 



